The invention relates to an interference suppression filter and lightning current diverter device in a coaxial line for transmitting high-frequency signals, comprising a housing with two connectors, the housing forming an outer conductor connected to ground, and an inner conductor guided through the housing, as well as a connection between inner conductor and housing.
Interference suppression filter and lightning current diverter devices of this type are known. They serve for the purpose of protecting assemblies, apparatus or installations connected to lines, for example coaxial lines of telecommunication devices, against electromagnetic pulses, overvoltages and/or lightning currents. Electromagnetic pulses of artificial type can be generated for example by motors, switches, clocked power supply units or also in connection with nuclear events, and pulses of natural origin can be formed, for example, as a consequence of direct or indirect lightning strikes. The known protective circuits are therein disposed on the input side of the assemblies, apparatus or installation, and these circuits can be diverting or reflecting systems.
An EMP diverter of this type is disclosed in EP 938 166. This EMP diverter comprises a housing serving as outer conductor and connected to ground. In a first portion of this housing, which extends in the direction of introduction axis of a coaxial cable, is carried an inner conductor. In a second housing portion, which projects at right angles from the first housing portion, is disposed a connection in the form of a λ/4 shortcircuit line, which connects the inner conductor with the housing. With this known T-configuration it is already possible to attain with suitable known geometric configurations and implementations very good protection of the connected apparatus, assemblies or installations. EMP diverters of this type must meet international standards and fulfill for example the test conditions according to the IEC Standard (International Electronic Commission).
In spite of the good effectiveness, diverters of this type have the disadvantage that a residual voltage, and therewith also a residual energy, is still delivered via the inner conductor to the connected assemblies, apparatus or installations. Since only one contact point of the shortcircuit line to the housing exists, the current carrying capacity is also limited. A further disadvantage comprises that the housing portion, incorporation the λ/4 shortcircuit conductor and arranged at right angles to the inner conductors, is relatively large and leads to a bulky constructional size of this diverter. The installation of such diverters often presents considerable difficulties due to the λ/4 shortcircuit conductor projecting at right angles, and appropriate distances between adjacent structural elements must also be maintained. This structural shape can also not be covered with shrinkable tubing against environmental effects, but rather, in practice, corrosion protection tape is wound around it. This leads to increased costs.
A diverter in a more compact mode of constructing is disclosed in DE 199 36 869. In this apparatus on the housing a chamber is attached, which is disposed in a tangential plane at a radial spacing and approximately parallel to the inner conductor. As a connection between inner conductor and housing, a shortcircuit conductor of specific length is located in this chamber in a circular or spiral configuration.
This implementation leads to a reduction of the radial structural dimensions of the apparatus. With this solution there is also the disadvantage that, due to the line inductance, residual voltage, and therewith also a residual energy, is transferred or is conducted further via the inner conductor. Since also only one contact point exists between shortcircuit conductor and housing, the capacity for carrying current is also limited.